The main objectives of this research proposal are to determine the sequence of morphological changes in ischemic injury, to relate them to the amount of blood flow at different sites and to define criteria of irreversible injury in the ischemic myocardium. The mitochondrial deposits are presumably associated with irreversible injury. These mitochondrial deposits as determined by x-ray microanalysis technique contain calcium, phosphorus or magnesium. Thus parallel studeis on cell membrane permeability and on the nature of mitochondrial deposits in unvixed frozen sections during early phases of ischemia will determine the sequence of alterations in the injured cell, the degree of alteration necessary to produce irreversible injury and the effect of interventions on preventing such changes. Reperfusion of ischemic myocardium with whole blood allows deposition of calcium in the mitochondrial matrix while with calcium-free blood no such deposits are seen and the cell membrane permeability remains unaltered. We hypothesize that calcium affects the structural integrity of the sarcolemma as shown by disruption of perimembrane, increased permeability, enzyme release and defect in the lipid bilayer. Therefore, we will investigate the effect of calcium overload on the sarcolemmal lipid bilayer and mitochondrial ionic contents. We plan to quantitate the degree of damage with SEM and TEM in the blood vessels during coronary occlusion and reperfusion. Finally, effects of therapeutic interventions alleviating the effects of calcium overload, energy exhaustion and electrolyte imbalance will be investigated in detail.